1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, a program thereof and a storage medium for storing the program.
2. Description of the Related Art
In general, documents to be read in a digital multifunction peripheral or the like are mainly classified into three types, that is, character documents, photographic documents, and halftone dot printed documents. A halftone dot printed document is a document on which an image having gradations is decomposed into fine dot aggregates so that the gradations are represented in a simulated manner by the size of dots per unit area, that is, an average concentration per unit area.
If such a document, or a mixed document of these is scanned, characters, halftone dots, photographs, etc., are identified, and processes suitable for the respective regions are performed. On the character region, a process that puts an emphasis on the resolution is performed so that character recognition and character vectorization processes are executed. On the halftone dot and photographic regions, a process that puts an emphasis on the gradation is performed to improve its image quality. For this reason, it is generally necessary that characters, halftone dots, and the like can be identified with high precision.
Japanese Patent Application Laid-Open No. 5-328143 has discussed a method in which characters, halftone dots, and the like are systematically identified by using a determination based on color information of a document image and a determination based on edge information. Japanese Patent Application Laid-Open No. 5-328143 has discussed a process in which a document image is divided into blocks, each composed of a predetermined number of pixels, and determinations are respectively made thereon as to whether any edge exists in the block and as to whether any restricted color exists in the block. Moreover, in the processing method of Japanese Patent Application Laid-Open No. 5-328143, a block in which any edge exists and any restricted color also exists is determined as a character block, and the other blocks are determined as non-character blocks.
In the determination method discussed in Japanese Patent Application Laid-Open No. 5-328143, however, since both of a determination as to characters or halftone dots based on color information and that based on edge information are combined with each other to perform the determination, an erroneous determination tends to occur in the attribute of a region if the determination result of a region based on the color information and the determination result of the attribute of a region based on the edge information are different from each other. As a result, it is not possible to perform appropriate image processing, with the result that the image quality of the processed image deteriorates to cause broken characters.